A liquid-crystal elastomer is a hybrid material of liquid-crystals and elastomers. The liquid-crystal elastomer shows a characteristic response behavior in such a manner that the liquid-crystal elastomer is extended in the orientation direction by applying an external stimulus such as heat, light, electric field, and magnetic field to increase the degree of liquid-crystal orientation, but the liquid-crystal elastomer is shrunk by removing such a stimulus to decrease the degree of liquid-crystal orientation. Thus, applications of such an elastomer to various fields such as actuators and the like have been attempted.
For example, Patent Document 1 discloses a high-molecular liquid-crystal polyurethane exhibiting liquid crystallinity, which is obtained by reacting a bis(ω-hydroxy-alkyleneoxy)biphenyl with 1,4-phenylene diisocyanate.
Further, Patent Document 2 discloses a polymer liquid-crystal polyurethane obtained by polymerizing a diol component having a mesogenic group with a trans-1,4-cyclohexane diisocyanate.
However, in the conventional liquid-crystal polyurethane, the temperature at which a liquid-crystal is developed is very high and it was difficult to develop liquid crystallinity at a low temperature (near room temperature). Further, the conventional liquid-crystal polyurethane did not exhibit rubbery elasticity due to increased fluidity when a liquid-crystal is developed therein. Further, the conventional mesogenic diol as a starting material has a high temperature at which liquid crystallinity is exhibited and was difficult to produce a liquid-crystal polyurethane without a solvent.